"A General Investigation of the Sensitiveness of Brushless Permanent Magnet Synchronous Machines Considering Magnet Tolerances"
, in IEEE Transactions on Magnetics, Vol. 56, Nummer 1, 2020, ISSN: 0018-9464
A General Investigation of the Sensitiveness of Brushless Permanent Magnet Synchronous Machines Considering Magnet Tolerances
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This article is about investigating the tolerance sensitiveness of electric machines regarding permanent magnet failures. The focus is on established permanent magnet synchronous machine designs in terms of slot and pole count. A finite-element-based approach is presented that allows analyzing single air-gap magnetomotive force (MMF) harmonics and the therefrom caused effects. Their corresponding magnitudes can be estimated based on a relatively fast analytical evaluation of multiple simultaneous magnet failures. Examples of evaluated magnet tolerances are misplaced permanent magnets or differences in the magnets' width, height, or magnetization strength, and direction. In contrast to investigating numerous different combinations of permanent magnet failures, general statements regarding the tolerance sensitiveness of the machines can be derived within reasonable time. A case study is defined, featuring six different topologies and the sensitivity on cogging torque and linked flux harmonics is evaluated. Low-order MMF harmonics are focused, as those typically feature the most significant impact on the machine's performance. Significant differences among the configurations regarding cogging torque increase and additional linked flux harmonics compared to the ideal structure are observed. The presented general technique can thus help engineers to rate the sensitivity of machine designs with regard to tolerance-induced MMF harmonics. The presented approach is thus useful at both the early design stage to select the most suitable machine configuration in terms of the number of slots, poles, and the winding arrangement, and during machine design optimization to compare different geometrical configurations.